Hopeit
| Hopeit | |
|---|---|
 (image width: 10 mm) |
|
| General and classification | |
| other names |
|
| chemical formula | Zn [6] Zn 2 [4] [PO 4 ] 2 • 4H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.CA.30 ( 8th edition : VII / C.11) 03/40/04/01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Room group (no.) | Pnma (No. 62) |
| Lattice parameters | a = 10.62 Å ; b = 18.43 Å; c = 5.02 Å |
| Formula units | Z = 4 |
| Frequent crystal faces | {010}, {110}, {031}, {131} |
| Physical Properties | |
| Mohs hardness | 3.5 |
| Density (g / cm 3 ) | measured: 3.05 to 3.065; calculated: 3.116 |
| Cleavage | completely after {010}; good after {100}; indistinct after {001} |
| Break ; Tenacity | uneven; brittle |
| colour | colorless, gray-white, yellow, orange |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass luster, pearlescent luster on the gap surfaces |
| Crystal optics | |
| Refractive indices |
n α = 1.572 to 1.574 n β = 1.582 to 1.591 n γ = 1.590 to 1.592 |
| Birefringence | δ = 0.018 |
| Optical character | biaxial negative |
| Axis angle | 2V = 26 to 82 ° (calculated) |
Hopeite is a rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the orthorhombic crystal system with the composition Zn [6] Zn 2 [4] [PO 4 ] 2 · 4H 2 O, so from a chemical point of view it is a water-containing zinc phosphate .
Hopeite mostly develops tabular to prismatic crystals , but is also found in the form of tufted, radiant or massive mineral aggregates or crusty coatings. Visible and unweathered crystal surfaces have a glass-like sheen , whereas cleavage surfaces have a mother-of-pearl shimmer. In its pure form, the mineral is colorless and transparent. However, due to multiple light refraction due to lattice construction defects or multicrystalline formation, it can also appear gray-white and take on a yellow to orange color due to foreign admixtures. However, its line color is always white.
Etymology and history
Hopeit was first discovered near "Altenberg" (today Kelmis ) in the Belgian province of Liège and described in 1824 by David Brewster , who named the mineral after the Scottish doctor and chemist Thomas Charles Hope (1766–1844).
classification
Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , Hopeit belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates without foreign anions ", where together with Fahleit , Parahopeit , phosphophyllite , Radovanit and Smolianinovit formed the independent group VII / C.11 .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns Hopeit to the class of "phosphates, arsenates and vanadates" and there to the department of "phosphates etc. without additional anions ; with H 2 O “. This division, however, is further divided according to the size of the participating cations , so that the mineral according to its composition in the subsection "With large and small / medium-sized cations" is to find where it is the only member of the unnamed group 8.CA.30 forms .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Hopeit to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc.". Here he is together with Rollandit in the "Hopeit Group" with the system no. 40.03.04 within the sub-section of " Water-containing phosphates etc., with (A 2+ ) 3 (XO 4 ) 2 × x (H 2 O) ".
Modifications and varieties
The compound Zn [6] Zn 2 [4] [PO 4 ] 2 · 4H 2 O is dimorphic , so it occurs in nature as triclinic crystallizing parahopeite in addition to the orthorhombic crystallizing hopeite .
Education and Locations
Hopeite forms in some hydrothermal zinc deposits and complex granitic pegmatites . Encrustations arise in bone breccias in limestone caves. Accompanying minerals include ferrisicklerite , hemimorphite , hydroxyapatite , laueit , leukophosphite , robertsite , smithsonite , spencerite , sphalerite , tarbuttite , triphyline and vanadinite .
As a rare mineral formation, Hopeit could so far (status: 2011) only be proven at a few sites. Around 20 sites are known to be known. and its type locality "Altenberg" (Kelmis) is the only known site in Belgium so far.
In Germany, the mineral occurred at Kreuzberg near Pleystein and in several places near Hagendorf / Waidhaus in Bavaria, in the Glücksrad mine in Lower Saxony, in the Büsbacherberg-Brockenberg ore mine in North Rhine-Westphalia and in the Friedrichssegen mine near Frücht in Rhineland-Palatinate on.
Other locations include Australia, Bolivia, China, Canada, Portugal, Zambia, Spain, South Africa and the United States of America.
Crystal structure
Hopeite crystallizes orthorhombically in the space group Pnma (space group no. 62) with the lattice parameters a = 10.62 Å ; b = 18.43 Å; c = 5.02 Å and 4 formula units per unit cell .
See also
literature
- David Brewster : Description of Hopeite, a new mineral, from Altenberg near Aix- la-Chapelle ( PDF 145.9 kB )
Web links
- Mineral Atlas: Hopeit (Wiki)
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 473 .
- ↑ Webmineral - Hopeite
- ↑ a b c d e John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Hopeite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64.6 kB )
- ↑ a b c d e Mindat - Hopeite